JPH1054920A - Optical fiber tap and optical array device provided with the optical fiber tap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently extract and distribute light propagating in a polymer optical fiber (POF). SOLUTION: At least one mirror is formed inside a polymer optical fiber. PO
At the location where the internal mirror is formed in F, light propagating in the POF strikes the mirror and is efficiently deflected from the polymer optical fiber. The deflected light is efficiently extracted and distributed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to the field of photonics, and more particularly, to optical fiber taps used in extracting and distributing light propagated through polymer optical fibers.

[0002]

2. Description of the Related Art Conventionally, various systems using optical fibers are well known, and are applied to an ever-increasing variety of applications. These systems include, for example, fiber optic communication systems, medical instruments, copiers, printers, facsimile machines, optical displays, and lighting.

[0003] As the use of optical fiber-based systems has increased, polymer optical fibers (POs) have replaced conventional glass optical fibers for many of the applications described above.
F) is being recognized as a cost-effective alternative. Regarding this, for example, F.S. "Novel Plastic image tr by Suzuki
announcement fiber, "(Proc. S.
PIE, 1592, pp. 112-132, (1991)
Year)); Brun, C .; Farget, M .; Reg
lat, M .; Druetta, J .; P. Goure,
J. P. "Plastic" by Montierd et al.
optical fiber for latera
l illumination: chemical
studiosand optical measure
elements, "(Proc. 4th International
tional Conf. Plastic Optic
alFibers & Applications, B
Oston, MA, Oct. 17-19, 1995,
187-192); Farenc, P .; Dest
Ruil, “Illumination, sig
negotiation, and decoratio
n using plastic optical f
ibers "(Proc. 4th Internet
ionical Conf. Plastic Optica
1 Fibers & Applications, B
Oston, MA, Oct. 17-19, 1995,
203-205); Sottini, D.M. Gra
ndo, L .; Palmetti, E .; Giorget
"Optical fiber-poly" by Ti et al.
mer guide coupling by at
apered graded index glass
guide "(IEEE J. of Quantu
Electronics, 31, 174-180 (1995)). Advantages of using POF include, for example, basic light weight, flexibility, resistance to breakage, low material costs, connection costs, and immunity to electromagnetic interference.

In many applications using POF, it is necessary to use an optical tap to extract a small amount of light propagating in the optical fiber from the optical fiber. That is, in a very large scale integrated (VLSI) multiprocessor system including an optical local area network (LAN), a small amount of light propagating in the optical fiber is extracted from the optical fiber to distribute the light to a large number of nodes. Requires the use of optical taps. The usefulness of such an optical tap is measured, for example, by the light loss due to the tap. The maximum number of taps is determined according to the magnitude of this loss, and thus the maximum number of stations that can be combined without requiring signal regeneration by a signal repeater.

[0005] Conventional fiber optic taps and techniques require at least one connector, and in general,
These techniques require breaking the optical fiber when forming the tap. Furthermore, in systems using optical fibers, when connecting and disconnecting taps,
Communication is often interrupted. In general, when designing optical taps, connector losses of 0.2-2.0 dB are inherent, which limits the number of taps that can be connected in a fiber distribution system.

In another optical fiber tap, there is no need to break the optical fiber or attach a connector, and power is coupled to a mode radiated from the optical fiber to extract light energy. Such an optical fiber tap is described, for example, in US Pat. No. 3,931,5.
No. 18, No. 3,936,631, and No. 3,982
No. 123. The comprehensive technology disclosed and claimed in these U.S. patents is to radiate light from the core of the optical fiber to the cladding, such as by bending the fiber, and to emit light from the fiber cladding and couple by a dielectric. Thereafter, detection is performed by the detection means.

[0007]

The conventional techniques used when tapping an optical signal propagating through an optical fiber are useful in many situations, but these conventional techniques are simple, efficient, and costly. As described above, there are some problems in terms of effects. Accordingly, it would be desirable to provide a method and apparatus for efficiently extracting and distributing light propagating through an optical fiber, and there is still a need in the art for such an implementation.

[0008] It is an object of the present invention to provide an optical fiber tap that can efficiently extract and distribute light propagating through a polymer optical fiber.

[0009]

According to the present invention, there is provided an optical fiber tap used for extracting light propagating through an optical fiber, the optical fiber tap being disposed in the optical fiber and having a predetermined length of light propagating through the optical fiber. And at least one mirror that deflects the predetermined portion outward from a side surface of the optical fiber when the portion hits the optical fiber tap. That is, an optical fiber tap according to the present invention comprises, for example, in addition to a polymer optical fiber (POF), at least one mirror formed from the POF itself and disposed between its ends within the polymer optical fiber.

According to one aspect of the present invention, there is provided a method and apparatus for efficiently extracting and distributing light propagating in a POF. In particular, when light propagating through the POF impinges on the mirror at the position where the internal mirror is formed in the POF, the light is efficiently deflected from the POF. Thereby, the deflected light can be efficiently extracted and used effectively.

According to another aspect of the present invention, there is provided a method and apparatus for efficiently entering and distributing light into an optical fiber. In particular, when light enters the optical fiber at the position where the mirror is disposed, the incident light is deflected by the mirror and propagates through the optical fiber.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. In the drawings, the same or similar components are denoted by the same reference numerals.

Referring first to FIG. 1A, there is shown a cutaway view of the optical assembly. A known polymer optical fiber (POF) 100 has light 140 and 14 propagating from opposite directions along the length of the POF, respectively.
5 are shown. The cut and refilled region 120 includes a plurality of interior mirrors 130 and 135, and the cut / refill region including the interior mirror is preferably microcut, masked, coated, and refilled. And so on.

Light propagating through the POF will be deflected upon hitting one of the internal mirrors. For example, light 140 propagating along the length of the POF is indicated by arrows 146 and 1
As shown at 44, they will be deflected against mirrors 130 and 135, respectively. Similarly, when light 145 strikes mirrors 130 and 135, respectively, the light will be deflected as indicated by arrows 142 and 148. The cut / refill area effectively functions as a port, or tap, so that the lights 142 and 1
44 can be emitted from the POF. One of ordinary skill in the art will readily recognize that this port is bidirectional, and light can be incident from the side of the optical fiber. In this case, the incident light impinges on the mirror and propagates along the length of the fiber, where it is distributed, ie, the next tapping by another tap.

FIG. 1 (c) shows how a tap according to the invention can be used as a tap to enter light into an optical fiber. That is, the lights 147 and 143 are incident on the optical fiber from the side, and one of the internal mirrors.
One surface. The light is deflected by the mirror and propagates along the length of the fiber as indicated by arrows 153 and 154. Two-way arrows 141 and 149
This shows that the direction of light propagating in the optical fiber can have bidirectionality.

As will become apparent below, a useful application of the present invention is to deliver optical signals of the same intensity to N different locations along the POF. That is,
For example, transmission of a computer clock or data signal.

In the above example, a POF having an arbitrary length is prepared. This POF is provided with N side emission ports along its length. The total intensity of the input light power is “1”, and the i-th output port has the coupling efficiency η _i
(1 ≦ i ≦ N), and the POF has a total length dependent transmittance exp.
Assuming that (−βl) (β and l represent the transmission coefficient and the fiber length, respectively), in order to achieve uniform light distribution at each of the N outgoing ports provided at regular intervals of Δl Uses the relationship of Equation 1.

[0018]

(Equation 1) If all N ports are distributed along a relatively short length of POF, the absorption dominant exponential term in Equation 1 can be omitted. In this case, η ₁ = 1 / N, η ₂ =
1 / (N−1),... Η _N−1 =. It is relatively easy to find that 05, η _N = 1. Once the individual coupling efficiencies are determined, the corresponding size of the internal mirror can be calculated.

FIG. 1B shows a cross section of a POF having a core 160 and a cut portion 170 (shown by hatching) in which a mirror is formed. The area of the mirror is related to the cut depth h of the cut portion. This cut depth can be easily measured during the cutting step. Using the parameters shown in FIG. 1B, the angle θ of the circular arc portion can be calculated by Expression 2.

[0020]

(Equation 2) Here, α = h / r is the relative depth of the cut portion. Within a first order approximation, the intensity in the large core POF is distributed evenly. The coupling coefficient η of the mirror is η = S / (π
r ² ).
Here, S is the area of the mirror (shown with diagonal lines in FIG. 1B), and r is the radius of the POF. The mirror area S is given by Equation 3.

[0021]

(Equation 3) Here, a is obtained by Expression 4.

[0022]

(Equation 4) Therefore, the relationship shown by Expressions 5 and 6 is established between η and α.

[0023]

(Equation 5)

[0024]

(Equation 6) Equations 1, 5, and 6 represent N along the length of the POF.
It can be used to determine the depth of the cut used to form the individual mirrors.

FIG. 2 shows a system suitable for forming a POF with an internal mirror according to the invention. That is, the POF 280 is a micrometer-controlled XY translation stage [controlled XY translational stage] 270.
It is fixed to. The blade 250 is mounted on the micrometer-controlled rotary translation stage 240, and is heated under the control of the thermoelectric heat controller 230. This blade 25
0 is used to cut the exact area from the POF and form an internal mirror. The blade used is, for example, a polished razor blade. Thermoelectric heat controller 2
By using 30, it is possible to accurately select the cutting temperature by the blade.

For example, satisfactory results were obtained when an internal mirror was formed on a polymethyl methacrylate (PMMA) fiber (Model TB-750) manufactured by Asahi Kasei Co., Ltd. The fiber core has a diameter of 750 μm and has a refractive index of n = 1.9944 at a wavelength λ = 650 nm. PMM
Material A is soft enough to cut at room temperature, but according to experimental results, by using a combination of pressure and blade temperature in the temperature range of 100-100 ° F,
It has been found that a better mirror finish is obtained, ie a surface roughness of less than 15 μm.

Preferably, PO is used during the cutting step.
One end of F is connected to a light source, ie, laser 260, and PO
The other end of F is connected to the digital optical power meter 290.
In this way, when the residual power output on the power meter side of the POF is monitored online, the intensity output of each mirror can be accurately controlled. Referring to FIG. 3, FIG. 3 shows an intensity profile of 16 mirror rows evenly formed along a 20 mm cross section of the PMMA fiber. The reflection was due to total internal reflection at the PMMA / air interface, as none of the mirrors had a metallic coating on the surface. Despite this fact,
A contrast ratio better than 15: 1 was obtained.

Those skilled in the art will readily appreciate that the residual optical power can be monitored not only at the output of the fiber but also at individual mirrors. Using this on-line monitoring technique, PMMA fibers having 200 side emission ports with less than 20% intensity variation per port were formed.

Referring to FIG. 4, Equation 1, Equation 5, and Equation 6
Is a graph comparing the value of the cutting parameter α calculated respectively with the value measured later. In this measurement, one was sampled for every five cut portions. In order to secure the strength of the fiber after forming the cut portion, the cut depth was selected so that α _{i = 200} = 0.25. In this fiber, the attenuation due to absorption was less important than if the light had to be distributed over longer distances. This is because the total length of the fiber was only 0.4 m.

Using a modification of the mirror forming method described above,
Cutting can be performed in parallel. That is,
Multiple blades with a given cutting angle and depth can be used simultaneously to speed up the entire manufacturing process. However, accurate control of light fluctuations becomes more difficult. Further, by fixing the position of the optical fiber and changing the direction of cutting, or changing the feed direction of the optical fiber while fixing the direction of cutting, the optical fiber can be moved in almost all directions in the three-dimensional space. Can be combined. This provides greater flexibility in the use of the finished optical fiber.

The mirror is curved (curved) even if it is flat.
It may be. Thus, light can be deflected from the optical fiber through the entire circumference of the optical fiber or a part thereof. Further, the light deflected from the optical fiber can be deflected at an angle smaller than a right angle with respect to the side of the fiber. In addition, depending on the application, the mirror can be partially reflective or partially transmissive.

As still another example of the present invention, a transparent polycarbonate plate having a thickness of 2 mm was machined, and ten parallel V-grooves were juxtaposed at an interval of 2 mm between two adjacent grooves. Next, a long PMMA fiber was bonded inside the groove. 100 mirrors were formed using the above-described cutting technique. Of course, mirrors that are later measured to be too small can be extended by additional cutting. Conversely, mirrors that are later measured to be too large can be partially or completely filled with a suitable material, ie, a material such as epoxy or PMMA. FIG. 5 shows 10.times.10 light spot patterns produced by the plate thus treated. That is, as described above, for example, when grooves are formed in a transparent polycarbonate plate, and optical fibers are arranged in these grooves, and the optical fibers are geometrically arranged in a predetermined pattern, light is emitted by a mirror. The light will be deflected out of the fiber to provide light illumination in the predetermined pattern described above.

Although the present invention has been described with reference to preferred embodiments, it is needless to say that various modifications can be made without departing from the spirit and scope of the present invention. For example, a well-known laser or other cutting device may be used instead of the mechanical blade described above. Similarly, the internal mirror need not be planar and can be any other suitable shape.

[0034]

As described above, according to the present invention, at least one internal mirror is formed in an optical fiber, and a predetermined portion of light propagating through the optical fiber is struck against the internal mirror, and a predetermined portion of the light is transmitted from the side surface of the optical fiber. Since the predetermined portion is deflected, the light propagating through the optical fiber can be efficiently extracted and distributed.

[Brief description of the drawings]

FIG. 1 (a) is a cutaway view of a polymer optical fiber (POF) having a micro-mirror formed inside, and FIG.
FIG. 3C is a cross-sectional view of the OF, and FIG. 3C is a cutaway view of the POF in which a micro mirror used for bidirectional light extraction / insertion is formed.

FIG. 2 shows an apparatus for forming a series of micro mirrors along the length of a POF.

FIG. 3 is a diagram showing the intensity of 16 light spots emitted along the length direction of a POF.

FIG. 4 is a diagram illustrating a coupling efficiency with respect to a cut depth of a mirror;

FIG. 5 shows the results obtained by using a POF manufactured according to the present invention;
FIG. 3 is a diagram showing light distributed along a × 10 light spot array.

[Explanation of symbols]

 100,280 Polymer optical fiber (POF) 140,145,147,143 Light (arrow) 130,135 Internal mirror 120 Cut / refill area 160 Core 170 Cut area 270,240 Micrometer controlled moving stage 250 Blade 260 Laser 290 Digital light Power meter

Claims (21)

[Claims] An optical fiber tap used for extracting light propagating through an optical fiber, wherein the predetermined portion of the light that is disposed in the optical fiber and propagates through the optical fiber hits the predetermined portion. An optical fiber tap comprising: at least one mirror deflecting outward from a side surface of the optical fiber. 2. The optical fiber tap according to claim 1, wherein the optical fiber is made of a polymer material. 3. The optical fiber tap according to claim 1, wherein the mirror is formed by cutting the optical fiber. 4. The optical fiber tap according to claim 3, wherein the mirror is coated with a reflective material to increase reflectivity. 5. The optical fiber tap according to claim 3, wherein a sharp instrument is used when forming the mirror. 6. The optical fiber tap according to claim 5, wherein the sharp instrument is heated when the optical fiber is cut to form the mirror. 7. The optical fiber tap according to claim 3, wherein a laser cutting device is used when forming the mirror. 8. The optical fiber tap according to claim 2, wherein the polymer material is polymethyl methacrylate (PMMA). 9. The optical fiber tap according to claim 3, wherein the optical fiber is coupled to a light source and a power meter, and the optical power is monitored by the power meter during cutting of the optical fiber. . 10. The optical fiber tap of claim 1, wherein the deflected light is deflected at a substantially right angle to a side of the optical fiber. 11. The optical fiber tap of claim 1, wherein said mirror is substantially planar. 12. The optical fiber tap according to claim 1, wherein the mirror has a substantially curved shape. 13. The optical fiber tap according to claim 1, wherein the deflected light is deflected and output from a predetermined portion of the entire circumference of the optical fiber extending from 0 ° to 360 °. 14. The optical fiber tap according to claim 1, wherein said mirror partially reflects said light. 15. The optical fiber tap of claim 1, wherein the mirror partially transmits the light. 16. The optical fiber tap according to claim 5, wherein a plurality of sharp instruments are used when forming the mirror. 17. An optical fiber tap used for distributing light in an optical fiber, the optical fiber tap including at least one mirror disposed in the optical fiber, wherein the light incident on a side surface of the optical fiber is reflected by the mirror. An optical fiber tap which is deflected by the optical fiber and propagates the light beam along the length direction of the optical fiber. 18. The optical fiber tap according to claim 17, wherein the optical fiber is made of a polymer material. 19. The optical fiber tap according to claim 18, wherein the mirror is formed by cutting the optical fiber. 20. The optical fiber tap of claim 19, wherein said mirror is coated with a reflective material to increase reflectivity. 21. At least one optical fiber geometrically arranged in a predetermined pattern, said optical fiber having at least one mirror disposed on each of said optical fibers, said mirror comprising: An optical array device, wherein a predetermined portion of light propagating through the optical fiber is deflected outward from a side surface of the optical fiber to obtain an optical illumination in the predetermined pattern.